Generally speaking an operation such as for example the positioning of working tools in a shaft under pressure requires the use of an introduction or withdrawal isolation chamber which must be connected to the head of the shaft. For this purpose the upper part of the head of the shaft is provided with an isolation chamber valve designed to enable the isolation chamber to be connected or isolated in relation to the shaft.
Isolation chamber valves may in particular be of the ball type, although these valves are not always suitable for the use for which they are intended.
It should be noted in particular that wear occurs on the sealing joints of the valve.
In fact when the isolation chamber valve is in the closed position, there are different pressures on either side of the valve ball. This difference in pressure is generally speaking very high and the operation of the ball, particularly when the valve is open becomes all the more difficult as it is necessary to avoid jumps in pressure so as not to damage the working tools it is desired to position in the shaft.
When it is operated, the valve ball is controlled by rotation and this causes a throttling of the flow of the fluid resulting in the serious deterioration of the sealing components. Consequently, repairs of varying frequency are required according to the frequency of operation of the valve.